Comparison
225/45 R18 vs 245/40 R17
Minus-sizing from 225/45 R18 to 245/40 R17 pairs a smaller 17-inch wheel with more rubber between the rim and road. This sizing approach swings rolling diameter far enough to feel on the road. The speedometer error is noticeable and may warrant a recalibration if you rely on indicated speed. Less sidewall flex usually translates to crisper turn-in and a slightly stiffer ride over rough pavement. Diameter delta falls in the cautious 3–5% range, where speedometer recalibration and a careful clearance check are worth doing.
TakePractical direction for winter wheels, chains, or rougher pavement where cushioning matters.
Quick math: 245/40 R17 is 31.9 mm shorter than 225/45 R18, shifting the speedometer by -4.84%.
Current Tire
New Tire
Ground line · scaled comparison
Slight Difference
Within ±5% — usable, recalibration recommended
Diameter change
-31.9 mm
-4.84%
Speedometer at 100
95.2 km/h
-4.84% error
Ground clearance
-16.0 mm
ride height delta
Sidewall change
-3.3 mm
revs/km: 507.0
Permalink for this comparison:
/compare/225-45-r18-vs-245-40-r17Detailed comparison
| Metric | 225/45 R18 | 245/40 R17 | Difference |
|---|---|---|---|
| Overall diameter | 659.7 mm | 627.8 mm | -31.9 mm (-4.84%) |
| Sidewall height | 101.3 mm | 98.0 mm | -3.3 mm |
| Circumference | 2.073 m | 1.972 m | -100.2 mm |
| Revs / km | 482.5 | 507.0 | +24.5 |
| Ground clearance | reference | -16.0 mm | -16.0 mm |
| Speedometer @ 100 km/h | 100.0 km/h | 95.2 km/h | -4.84 km/h |
Verdict: warning
Between 3% and 5% — noticeable speedometer drift; recalibration may be advisable.
Speedometer impact
At a true 100 km/h, your dashboard will read 95.2 km/h after switching to 245/40 R17 — a -4.84% offset. Use the speedometer error calculator to recheck for other indicated speeds, and the speedometer error guide for the full background.
Ground clearance change
The new tire's half-diameter changes ride height by -16.0 mm. Small differences are absorbed by suspension travel, but anything beyond ±10 mm can affect headlight aim, fender clearance and bump-stop margin. See the plus-sizing guide before committing.
Back to
225/45 R18
Back to
245/40 R17
Drivers also compare
Closely-related fitments and plus-size swaps for 225/45 R18 and 245/40 R17.
225/45 R18 vs 255/40 R18
Wider variation on the same rim — more grip, less clearance.
Δ 0.23%
215/45 R17 vs 245/40 R17
Wider variation on the same rim — more grip, less clearance.
Δ 0.40%
225/45 R18 vs 245/40 R18
Wider variation on the same rim — more grip, less clearance.
Δ 0.99%
225/45 R17 vs 245/40 R17
Wider variation on the same rim — more grip, less clearance.
Δ 1.02%
245/40 R17 vs 255/40 R17
Wider variation on the same rim — more grip, less clearance.
Δ 1.27%
225/45 R18 vs 235/45 R18
Wider variation on the same rim — more grip, less clearance.
Δ 1.36%
215/45 R18 vs 225/45 R18
Wider variation on the same rim — more grip, less clearance.
Δ 1.38%
205/50 R17 vs 245/40 R17
Wider variation on the same rim — more grip, less clearance.
Δ 1.41%
Related topics